This invention relates to the art of electronic control apparatus.
The present invention relates to control apparatus comprising at least one electrically-conductive target portion, and a position sensor in the form of an electromagnetic device arranged in proximity with the said at least one electrically-conductive target portion to provide a signal indicative of an attribute of the position of that portion relative to a portion of the electromagnetic device, and control means connected to receive such a signal from the electromagnetic device and to respond in dependence upon that signal, in which the electromagnetic device comprises electrically-conductive coil means, electrical pulse generating means connected to the coil means to deliver electrical pulses thereto, and measuring means also connected to the coil means to measure the voltage or other electrical parameter across the coil means at a predetermined time interval after each pulse.
Such apparatus is described in U.S. Pat. No. 5,712,563. This apparatus comprises a conventional variable inductance device.
The present invention seeks to provide apparatus with improved accuracy.
Accordingly, a first aspect of the present invention is directed to control apparatus having the construction set out in the opening paragraph of the present specification, in which the electromagnetic device is a pulse induction device, so that, subsequent to a pulse, the decay of the voltage or other electrical parameter across the coil means is slowed in relation to what it would have been had the electrically-conductive target been absent, and in which the measuring means are such as to provide a measure of the voltage or other electrical parameter across the coil means at a time when that measure would have been substantially zero had the target been absent, so that the excitation energy has died away.
The pulse induction device may comprise at least two coil portions which are spaced apart from one another or which diverge from one another, the portions defining a volume with the coil portions surrounding that volume, and the latter extending between those portions, the target portion and/or the coil portions being movable whilst the target portion remains within that volume, the electrical pulse generating means being connected to both the said at least two coil portions to deliver electrical pulses thereto, and the measuring means being connected to both the said at least two coil portions to provide a measure of the voltage or other electrical parameter across the coil portions, and thus to provide a signal indicative of an attribute of the position of the target portion within the said volume relative to the coil portions.
The target portion may be movable. It may be fixed relative to an accelerator pedal, with the- control apparatus comprising an engine, and the control means comprising a device for varying the speed of the engine in dependence upon the signal it receives from the pulse induction device
According to a second aspect of the present invention, there is provided a position sensor characterised by coil means in the form of at least two electrically-conductive coil portions, which are spaced apart from one another or which diverge from one another, these portions defining a volume with the coil portions surrounding that volume and the latter extending between those portions, electrical pulse generating means connected to the coil portions to deliver electrical pulses thereto, and measuring means also connected to the coil portions to provide a measure of the voltage or other electrical parameter across the coil portions, so as to provide a signal, the magnitude of which is substantially proportional to an attribute of the position of an electrically-conductive target portion within the said volume relative to the coil portions when the sensor is in use, the coil portions, electrical pulse generating means and the measuring means together constituting a pulse induction device, so that, subsequent to a pulse, the decay of the voltage or other electrical parameter across the coil portions is slowed in relation to what it would have been had the electrically-conductive target been absent, and in that the measuring means are such as to provide a measure of the voltage or other electrical parameter across the coil portions at a time when that measure would have been substantially zero had the target been absent, so that the excitation energy has died away.
The at least two coil portions may be spaced apart portions of a single coil, which is preferably elongate along its axis of winding or alternatively transversely of its axis of winding.
Alternatively, the said two coil portions may be independently energisable, and the electrical pulse generating means may be such as to apply pulses to the two coil portions alternately in such a manner that there is no pulse delivered to one of the coil portions when the other is being energised, and vice versa, and, in such a manner that there is a delay period between each pulse to enable the voltage or other parameter across each coil portion to be measured without interference from the other coil portion.
Preferably, each coil portion is in the shape of a right-angled quadrilateral.
Preferably, respective parts of the two coil portions are adjacent or contiguous, and preferably the two coil portions are set at an angle in the range from 50xc2x0 to 170xc2x0 to one another, preferably in the range from 95xc2x0 to 150xc2x0, most preferably about 100xc2x0. This provides the benefit of an output signal from the induction device being substantially linear with respect to a relative displacement of the said electrically-conductive target portion in a direction which is transverse of the said contiguous sides.
It is possible to thereby obtain a range of movement with a linear response say for the target portion which is four times that for a single coil arrangement, whilst the coil arrangement might be no more than one and a half times as large.
The two coil format permits a compact sensor to be constructed, and in particular reduces the size of the coils. This is highly beneficial in avoiding significant influence from the materials surrounding the sensor in use, for example mounting brackets and structural metal work. The coils cannot inherently distinguish between an intended target and any other conductive material within range, but small coils diminish this range.
Further, the two coil format provides cancellation of such interfering effects where both coils are being affected. Complete cancellation is obtained if such interfering effects are equal in each coil.
The combined effect of small coils and the tendency to cancel interference effects typically permits an unshielded dual coil sensor to be mounted directly to steel structures with minimal constraints.
Coils are a form of antenna, and keeping the coils small substantially reduces the reception of electromagnetic interference.
The cancellation effect also permits the incorporation of close fitting metal shielding within the sensor where external interference effects (structural or electromagnetic) would otherwise be unacceptable.
Position attributes in two degrees of freedom of relative movement of the target portion can be ascertained if the position sensor has two pairs of coil portions, each pair having the features of the said at least two coil portions, and the two pairs being arranged orthogonally in relation to one another.
According to a third aspect of the present invention, there is provided a position sensor comprising an electrically-conductive coil portion, electrical pulse generating means connected to the coil portion to deliver electrical pulses thereto, and measuring means also connected to the coil portion to provide a measure of the voltage or other electrical parameter across the coil portion, and thus to provide a signal indicative of an attribute of the relative position of an electrically-conductive target portion in relation to the coil portion, in which the target portion is hollow, and relative movement is possible between the target portion and the coil portion, with the coil portion remaining within the target portion, when the sensor is in use, and in that the electrical pulse generating means constitute a pulse induction device, so that, subsequent to a pulse, the decay of the voltage or other electrical parameter across the coil portion is slowed in relation to what it would have been had the electrically-conductive target been absent, and in that the measuring means are such as to provide a measure of the voltage or other electrical parameter across the coil portion at a time when that measure would have been substantially zero had the target been absent, so that the excitation energy has died away.
Such constructions are useful for instrumentation of pneumatic and hydraulic cylinders.
In each of the said first, second and third aspects of the present invention, it will be appreciated that the coil portion or portions and/or the target portion may be movable.